When the elements are arranged on the Periodic Table, certain characteristics of atoms show trends within the groups and periods.
These trends are observed as a gradual increase or decrease in the value of these characteristics.

The trending of these characteristics is dependent on two properties of atoms:
1.
The highest energy level that contains electrons
= each period adds another energy level around the nucleus
2.
The number of protons and electrons in the atom
= the more protons and electrons in the atom, the stronger the attractive force

There are 4 characteristics of atoms that we will study trends for:
1.
2.
3.
4.
Atom Size
Ionization Energy
Ion size
Electronegativity

Going Down a Group
Why do atoms get bigger going down a group?

Going Down a Group
Why do atoms get bigger going down a group?
Each period down adds another energy level around the nucleus, increasing the size of the atom

Going Down a Group
Why do atoms get bigger going down a group?
Each period down adds another energy level around the nucleus, increasing the size of the atom
Going Across a Period
Why do atoms get smaller going left to right across a period?

Going Down a Group
Why do atoms get bigger going down a group?
Each period down adds another energy level around the nucleus, increasing the size of the atom
Going Across a Period
Why do atoms get smaller going left to right across a period?
The number of protons increases moving across a period, increasing the attraction between the nucleus and the electrons. This attraction shrinks the atom.

The higher the ionization energy for an atom, the harder it is to remove an electron from the atom.
The lower the ionization energy for an atom, the easier it is to remove an electron from that atom.

Going Down a Group
Why is it easier to remove electrons from atoms further down a group?

Going Down a Group
Why is it easier to remove electrons from atoms further down a group?
The atoms are larger and electrons are farther from the nucleus. This makes the electrons easier to remove.

Going Down a Group
Why is it easier to remove electrons from atoms further down a group?
The atoms are larger and electrons are farther from the nucleus. This makes the electrons easier to remove.
Going Across a Period
Why is it harder to remove electrons as you move left to right across a period?

Going Down a Group
Why is it easier to remove electrons from atoms further down a group?
The atoms are larger and electrons are farther from the nucleus. This makes the electrons easier to remove.
Going Across a Period
Why is it harder to remove electrons as you move left to right across a period?
The atoms are smaller moving right across the periodic table with electrons closer to the nucleus. This makes the electrons harder to remove.

An ion is an atom that has lost or gained an electron(s).

An ion is an atom that has lost or gained an electron(s).
Metals have low ionization energies and
lose electrons easily. Metal ions are smaller than the original atom since they lost electrons.
Nonmetals have high ionization energies and gain electrons easily. Nonmetal ions are larger than the original atom since they gained electrons.

Even though the size of ions increases when moving from metals to nonmetals across a period, the overall trend for both metals and nonmetals is a decrease in ionic size.

Going Down a Group
What is the trend for electronegativity going down a group?

Going Down a Group
What is the trend for electronegativity going down a group?
Electronegativity decreases moving down a group

Going Across a Period
What is the trend for electronegativity going right across a period?

Going Across a Period
What is the trend for electronegativity going right across a period?
Electronegativity increases moving right to left across a period.

Answer the following questions:
1. Which element has the largest atomic size?
Li Na Be
2. Which element has the lowest ionization energy?
S Se Cl
3. Which element has the highest electronegativity?
C N Si